I find Echinacea interesting because its effects our endocannibinoid system, the same system marijuana effects ;)

The ECS effects pain, memory, immune systems, body temperature, muscle control, sleep, metabolic rate (which in turn effects nearly everything else)... its a pretty well connected part of the brain it seems.

Random stoner advice: if you're quitting marijuana and don't want to deal with the insomnia that comes from that, start popping Echinacea. I've found 3 days of restless sleep reduces to ~1 night of sort-of-not-great sleep if you start dosing with Echinacea to help your body get at least some of the chemicals its become dependent on while you're detoxing.

edit... just wanted to add I find anything claiming to be a "cure for cancer" to be skeptical. I like Echinacea, its a pretty cool plant, but I'll need to see more studies related to its effects on aging and cancer before I'd believe it has clear and measurable benefits for it... seems like someone would have figured it out a long time ago if the cure was sitting on a shelf in Walmart all this time :P